1. Field of the Invention
The present invention relates a method for manufacturing a heat transfer member for a heat exchanger by press forming a material to be worked, and specifically to a method for manufacturing the heat transfer member by subjecting the material to be worked to the plural press forming to obtain a plurality of patterns of irregularities arranged.
2. Description of the Related Art
The heat transfer member of the heat exchanger, which is generally formed of a metallic sheet, is press-formed into a prescribed shape, thus providing a finished product, which is to be put into practice. With respect to manufacture of the heat transfer member with the use of the press-forming device, a set of metallic molds have conventionally been used. More specifically, the material to be worked is held between the molds. Motion of moving the molds closely to each other has formed a pattern of irregularities serving as the heat transfer face on the metallic thin sheet of the material to be worked.
The press forming of the heat transfer member has conventionally been carried out in this manner. A set of molds forms the pattern of irregularities of the whole heat transfer member. It is therefore impossible to form any pattern of irregularities having a size larger than the molds. As a result, there is a restriction that the size of the heat transfer member depends on the size of the molds, thus making it impossible to manufacture the heat transfer member having a large area due to limitation of the size of the molds.
The metallic thin sheet used as the material for the heat transfer member, which has been coiled, has no linear property by which the longitudinal opposite side edges are in parallel with each other, due to heterogeneity in stress distribution and distraction during a rolling process, with the result that the metallic thin sheet is slightly curved into the so-called xe2x80x9cbanana-shapexe2x80x9d. Formation of the elongated heat transfer member with the use of the banana-shaped metallic thin sheet causes a problem that a plurality of press-forming positions cannot accurately been determined from the longitudinal opposite side edges and an accurate press forming cannot be carried out.
An object of the present invention, which was made to solve the above-mentioned problems, is therefore to provide a method for manufacturing a heat transfer member, which permits to apply the plural press forming on the material to be worked, utilizing a press-forming device, to form a plurality of prescribed patterns of irregularities as arranged, and permits to manufacture easily the heat transfer member having a large heat transfer face than an area of the mold by forming the proper irregularities on the elongated material.
In order to attain the aforementioned object, a method of the present invention for manufacturing a heat transfer member comprises the steps of:
subjecting material to be worked, which is made of a metallic thin sheet, to a press forming utilizing upper and lower molds of a press-forming devices to form said material into a shape having prescribed irregularities, thereby preparing a heat transfer member for a heat exchanger,
wherein:
an elongated material is used as said material to be worked;
a press-forming device is provided with molds each having a length shorter than said elongated material; and
said press forming is carried out by press-forming, while feeding said elongated material in a single feeding direction in parallel with a longitudinal direction of said elongated material, said elongated material on prescribed portions thereof, which have been previously set so as to be placed at prescribed intervals in the longitudinal direction of said elongated material, utilizing said press-forming device, thereby preparing the heat transfer member having a plurality of patterns of irregularities, which are arranged in the longitudinal direction of said elongated material.
In the present invention, the plural press forming is carried out, while moving the elongated material to be worked with the use of the prescribed press-forming device, to form a plurality of prescribed patterns of irregularities side by side. It is therefore possible to carry out an appropriate press forming on the entirety of the elongated material to be worked. As a result, the elongated heat transfer member having a larger size than the mold can be manufactured in a reliable manner, thus permitting manufacture of a heat exchanger, which has the large heat transfer member to enhance the heat exchange effectiveness.
In the second aspect of the present invention, as an occasion demands, a plurality of additional press-forming devices each being provided with molds having a length shorter than said elongated material to be worked may be provided so as to be arranged in a feeding direction of said elongated material to be worked on upstream and downstream sides of said press-forming device; and a press-forming may be applied, before and after the press forming on the portions of the elongated material to be worked utilizing said press-forming device, to both prescribed regions on one longitudinally extending side edge portion of the elongated material to be worked and prescribed regions on an other longitudinally extending side edge portion thereof utilizing any one of said additional press-forming devices, thereby preparing the heat transfer member having at least two kinds of patterns of irregularities, which are arranged in the longitudinal direction of said elongated material to be worked.
According to the features of the second aspect of the present invention, the press-forming is applied to the one longitudinally extending side edge portion of the material to be worked with the use of any one of the additional press-forming devices and also to the other longitudinally extending side edge portion of the material to be worked with the use of any one of the additional press-forming devices, so as to form the patterns of irregularities, which are different from the pattern of irregularities of the longitudinally extending central portion of the material to be worked. Such patterns of irregularities are arranged in combination with the other pattern of irregularities. It is therefore possible to carry out an appropriate press forming on the elongated material to be worked to form the optimum patterns of irregularities serving as a heat transfer section. It is also possible to form heat transfer sections in which the heat exchanging capacity is optimized, on the longitudinally extending opposite edge portions having required conditions, which are different from the longitudinally extending central portion. Continuous forming steps can also be carried out with the use of the press-forming devices as arranged, thus improving remarkably the forming operation efficiency.
In the third aspect of the present invention, as an occasion demands, the method may further comprise the step of forming flange portions on longitudinally extending opposite edge portions of the material to be worked so as to make a difference in level from a longitudinally extending central portion thereof, utilizing said press-forming device.
According to the features of the third aspect of the present invention, the flange portions are formed on the longitudinally extending opposite edge portions of the material to be worked, by means of the press-forming device, thus imparting a prescribed bending strength in the longitudinal direction to the material to be worked. Accordingly, even when the material to be worked is elongated, it does not easily bend. It is therefore possible to maintain properly the shape of the material as worked to facilitate the subsequent steps and increase the strength of the heat transfer member.
In the fourth aspect of the present invention, as an occasion demands, the method may further comprise the step of: forming flat portions having a prescribed width on longitudinally extending opposite edge portions of the material to be worked so as to make a difference in level from a longitudinally extending central portion thereof, as well as any set of prescribed recess portions and prescribed projection portions on said flat portions at prescribed intervals in the longitudinal direction of the material to be worked, utilizing said press-forming device.
According to the features of the fourth aspect of the present invention, the flat portions and the recess portions or the projection portions are formed on the longitudinally extending opposite edge portions of the material to be worked, by means of the press-forming device so that the flat portions serve as an area to which a subsequent connecting step is to be applied. When the material to be worked, which has been subjected to the press forming, is finally welded to the other material to be worked to form a heat transfer member, it is possible to utilize the flat portions as the area to which the welding step is to be applied, facilitating a welding operation. In addition, the material to be worked can be held by clamping the flat portions from opposite sides of the material to be worked in its transverse direction, thus providing an easy conveying operation of the material to be worked. Further, forming the recess portions or the projection portions on the flat portions of the material to be worked imparts the bending strength in the transverse direction to the material to be worked. Accordingly, the flat portions do not easily bend in the transverse direction of the material to be worked so as to prevent the material to be worked from bending in the transverse direction when holding it, while clamping the flat portions thereof.
In the fifth aspect of the present invention, as an occasion demands, the method may further comprise the steps of:
detecting, prior to the press forming of said material to be worked utilizing said press-forming device, any one of surface condition and internal structure of said material to be worked utilizing a detection device to obtain detection data;
analyzing said detection data utilizing a data analyzing device to judge existence of defects on any one of a surface and an inside of said material to be worked; and
in case where there is made a judgment that the defects exist on said material to be worked, stopping a feeding operation of the material to be worked to the press-forming device, removing respective portions having the defects from a downstream side and a upstream side of said defects of the material to be worked, and then feeding the material to be worked to the press-forming device, while detecting new defects after said defects in the feeding direction of the material to be worked utilizing said detection device.
According to the features of the fifth aspect of the present invention, an image of the material to be worked is previously captured by means of an imaging device, prior to the press forming, so as to check the existence of defects on the surface of the material to be worked, and in case where any defects exist, the material to be worked, from which the portion having the defects has been removed, is fed to the press-forming device in a free state of defects. It is therefore possible to avoid problems that the defects are recognized after press-forming the material to be worked by means of the press-forming device and such a press-formed material is identified as an improperly finished product, resulting in waste of the material to be worked. Feeding the material to be worked, from which the portion having the defects has been removed in a reliable manner, to the press-forming device makes it possible to prevent the defects from being erroneously left on the heat transfer member after the press forming thereof, thus ensuring safety.
In the sixth aspect of the present invention, as an occasion demands, the method may further comprise the steps of:
putting, prior to the press forming of said material to be worked utilizing said press-forming device, a plurality of marks for defining prescribed positions of the material to be worked to which the press forming is to be applied, on a surface of the material to be worked at prescribed intervals in the longitudinal direction of the material to be worked, utilizing a marking device; and
conducting the press forming on the prescribed positions of the material to be worked, which are defined by said marks, utilizing said press-forming device, when said marks of the material to be worked, which is fed in the single feeding direction, are detected by means of a mark detection device.
According to the features of the sixth aspect of the present invention, the marks for defining the positions of the material to be worked to which the press forming is to be applied, are previously put by means of the marking device, prior to the press forming. While detecting the marks by means of the mark detection device of the press-forming device, the press forming is applied to the material to be worked, in accordance with the marks as put so that the patterns of irregularities are formed on the portions of the material to be worked, on which the marks are put. It is therefore possible to carry out the press forming on the appropriate positions of the material to be worked, while obtaining information on the positions to which the press forming is to be applied, so as to make a precise positional adjustment for the press forming, thus improving accuracy of the shape of the heat transfer member as manufactured.